U.S. patent application number 14/255381 was filed with the patent office on 2015-10-22 for bidirectional dc converter-based battery simulator.
This patent application is currently assigned to Ford Global Technologies, LLC. The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to Ben A. Tabatowski-Bush, Tuyen Q. TRAN.
Application Number | 20150301120 14/255381 |
Document ID | / |
Family ID | 54321851 |
Filed Date | 2015-10-22 |
United States Patent
Application |
20150301120 |
Kind Code |
A1 |
TRAN; Tuyen Q. ; et
al. |
October 22, 2015 |
Bidirectional DC Converter-based Battery Simulator
Abstract
A battery simulator is configured to provide large energy pulses
for hot plug testing while maintaining the ability to quickly
respond during random order testing. A simulator can comprise a
plurality of cell simulators "cellsims" coupled to a DC power
supply. Each cellsim can include a bidirectional DC converter, a
bulk capacitor on the primary side of the converter, and a
switchable discharge capacitor on the secondary side of the
converter. The bidirectional DC converter enables the simulator to
cooperate with a battery control module (BCM) to perform active
cell balancing. Energy received from the BCM can be stored at the
bulk capacitor. The discharge capacitor can be coupled to an output
link to provide a high energy pulse to the BCM to simulate hot plug
conditions, and can be decoupled from the link during random order
testing. Output link voltage and current can be monitored for fault
detection.
Inventors: |
TRAN; Tuyen Q.; (Dearborn,
MI) ; Tabatowski-Bush; Ben A.; (South Lyon,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies,
LLC
Dearborn
MI
|
Family ID: |
54321851 |
Appl. No.: |
14/255381 |
Filed: |
April 17, 2014 |
Current U.S.
Class: |
324/434 |
Current CPC
Class: |
H01M 2010/4271 20130101;
B60L 2210/10 20130101; Y02T 10/72 20130101; G01R 31/3828 20190101;
G01R 31/2848 20130101; G01R 31/367 20190101; B60L 2270/20 20130101;
G01R 31/396 20190101; H01M 10/4207 20130101; H01M 2220/20 20130101;
B60L 3/0084 20130101; B60L 2250/10 20130101; Y02E 60/10
20130101 |
International
Class: |
G01R 31/36 20060101
G01R031/36 |
Claims
1. A system, comprising: a battery control module (BCM) configured
to monitor charge of one or more cells of an electrified vehicle
(EV) traction battery; and a simulator, configured for
bidirectional energy exchange with said BCM, configured to simulate
operation of said traction battery.
2. The system of claim 1, wherein said simulator comprises a
bidirectional DC/DC converter.
3. The system of claim 2, wherein said simulator comprises a
discharge capacitor configured to store energy received from said
bidirectional DC/DC converter and release said stored energy to
said BCM during a hot plug test.
4. The system of claim 3, further comprising a bulk storage
capacitor.
5. The system of claim 1, wherein said BCM and said simulator are
configured to perform active cell balancing.
6. A battery simulator, comprising: a power supply; one or more
cell simulators (cellsims) coupled to said power supply, each said
cellsim configured to simulate a cell of an electrified vehicle
(EV) traction battery; and wherein at least one of said cellsims is
configured for bidirectional energy exchange with a battery control
module (BCM) configured to monitor said traction battery
charge.
7. The battery simulator of claim 6, wherein each said cellsim
comprises a bidirectional DC/DC converter.
8. The battery simulator of claim 6, further comprising at least
one cellsim control module (CCM), each said CCM configured to
control operation of at least one of said cellsims.
9. The battery simulator of claim 8, wherein said CCM is configured
to monitor current between said cellsim and said BCM.
10. The battery simulator of claim 6, configured to cooperate with
said BCM to perform active cell balancing.
11. The battery simulator of claim 6, wherein said active cell
balancing comprises a donor cellsim providing energy to said BCM,
and a receiver cellsim receiving said energy from said BCM.
12. The battery simulator of claim 6, configured to store energy
received from said BCM at a bulk capacitor.
13. The battery simulator of claim 6, wherein at least one said
cellsim comprises a discharge capacitor switchably coupled to a
bidirectional DC converter, said discharge capacitor configured to
controllably release energy to a link coupling said cellsim and
said BCM.
14. A battery simulator, comprising: a power supply; and at least
one cell simulator (cellsim), said cellsim configured to simulate
an energy cell of an electrified vehicle (EV) traction battery,
said cellsim comprising a discharge capacitor switchably controlled
to provide energy to a battery control module (BCM) for said
traction battery.
15. The battery simulator of claim 14, wherein said discharge
capacitor is coupled to a link between said cellsim and said BCM to
hot plug test said BCM, and decoupled from said link to simulate an
electric vehicle drive mode condition of said traction battery.
16. The battery simulator of claim 14, further comprising at least
one cellsim control module (CCM) configured to control operation of
at least one said cellsim.
17. The battery simulator of claim 14, wherein said cellsim
comprises a DC/DC converter configured for bidirectional energy
transfer with said BCM.
18. The battery simulator of claim 14, wherein said discharge
capacitor is switchably coupled to a DC/DC converter.
19. The battery simulator of claim 14, wherein said discharge
capacitor is switchably coupled to a voltage bus configured to
couple said DC/DC converter to said BCM.
20. The battery simulator of claim 14, wherein said simulator is
configured to monitor said cellsim output and provide a fault
response when said cellsim output indicates a fault condition.
Description
FIELD OF INVENTION
[0001] This invention relates generally to battery simulators, and
more particularly to battery simulators designed to simulate
operation of a traction battery for an electrified vehicle.
BACKGROUND OF INVENTION
[0002] In electrified vehicles, a high energy storage device
provides traction power for motoring operations. In many cases the
energy storage device is in the form of a high voltage battery,
such as a lithium-ion battery, composed of a plurality of
electrically coupled energy cells. Typically, a battery control
module is coupled to a traction battery to monitor battery cell
charge. To decrease test and evaluation costs, a battery simulator,
rather than an actual traction battery, is often used to test a
battery control module. A battery simulator is composed of a
plurality of electronic devices designed to simulate the activity
of a plurality of battery cells. To test a battery control module
for a 36-cell battery, a battery simulator or battery tester
designed to simulate 36 cells is used. A script based on a record
of an actual vehicle drive cycle can be used put the simulator and
control module through the fluctuating energy demands placed on an
actual EV battery.
[0003] In the prior art, the capacity of a battery simulator to
test a battery control module under a variety of operational
conditions is somewhat limited by design constraints. For example,
many simulators employ a low voltage power source that may only
provide around 4-5 amps of current, much lower than the current
typically provided by an actual traction battery. Some simulators,
relying on very large sized capacitors to simulate energy storage
capacity, may have slow response times when subjected to quick,
random order testing. When optimized to better simulate vehicle
dynamics and response times, a simulator may fail to represent
energy storage capacity of a real battery cell. For example,
simulators often provide lower energy pulses to a battery control
module than those provided by an actual battery, reducing their
effectiveness for hot plug testing of a battery control module. As
a result, battery control modules that successfully pass tests
conducted with a battery simulator are often damaged by inrush
current when connected to an actual traction battery at a vehicle.
Finally, battery simulators usually include a unidirectional DC
converter configured to provide energy from the simulator to a
control module, where the energy is typically dissipated as heat.
Contemporary EV battery control modules can be designed for active
self-balancing in which energy from one battery cell can be
provided to a different battery cell. To test a battery control
module configured for active self-balancing, it is desired that a
battery simulator be configured to simulate the charge balancing
process. Simulation of energy transfer between battery cells is not
possible with prior art simulators designed to transfer energy only
from a simulated cell to a battery control module.
SUMMARY OF THE INVENTION
[0004] An example system includes a battery control module (BCM)
configured to monitor charge of one or more cells of a traction
battery for an electrified vehicle, and a battery simulator,
configured for bidirectional energy exchange with said BCM,
configured to simulate operation of the traction battery. Because
the battery simulator is configured for bidirectional energy
exchange with the BCM, it can be used to test BCM active
self-balancing capability.
[0005] An example battery simulator can include a plurality of cell
simulators (cellsims) coupled to a power supply, with each cellsim
configured to simulate a cell of an electrified vehicle (EV)
traction battery. At least one of the cellsims is configured for
bidirectional energy exchange with a BCM. In an example embodiment,
each cellsim comprises a bidirectional DC/DC converter configured
for energy exchange with the BCM and is configured to cooperate
with the BCM to perform active cell balancing.
[0006] In an example embodiment, a battery simulator comprises a
plurality of cellsims, with each cellsim comprising a discharge
capacitor that is switchably coupled to an output link between the
cellsim and the BCM. When the discharge capacitor is switched on,
it is coupled to an output link. Energy stored in the discharge
capacitor can be released to a battery control module, simulating
the release of a high energy pulse that can occur when a battery
control module is plugged into a battery pack. The ability to
provide such a pulse makes the present simulator suitable for hot
plug testing of a battery control module. When the discharge
capacitor is switched off, i.e decoupled from the output link, the
battery simulator can provide the dynamic response of a traction
battery during a vehicle drive cycle. Thus, a battery simulator of
the invention can represent energy storage characteristics of a
battery cell, as well as provide quick responses during random
order testing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 shows an example system of the invention.
[0008] FIG. 2 shows an example battery simulator.
[0009] FIG. 3 shows an example battery simulator circuit.
[0010] FIG. 4 shows a flow diagram of an example method for hot
plug testing a battery control module.
[0011] FIG. 5 shows a flow diagram of an example method for testing
a battery control module under vehicle drive mode conditions.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0012] Example embodiments of the invention are presented herein;
however, the invention may be embodied in a variety of alternative
forms, as will be apparent to those skilled in the art. To
facilitate understanding of the invention, and provide a basis for
the claims, various figures are included in the specification. The
figures are not drawn to scale and related elements may be omitted
so as to emphasize the novel features of the invention. Structural
and functional details depicted in the figures are provided for the
purpose of teaching the practice of the invention to those skilled
in the art, and are not to be interpreted as limitations. For
example, control modules for various systems can be variously
arranged and/or combined and may not be depicted in illustrations
of example embodiments herein in order to better emphasize novel
aspects of the invention. In addition, system components can be
variously arranged as known in the art.
[0013] Turning now to the several Drawings, in which like reference
numerals refer to like elements throughout the several views, FIG.
1 shows a system 10 in which a bidirectional battery simulator
(BBS) 12 is coupled to a battery control module (BCM) 14. As
indicated by the pair of opposing arrows, energy can be transferred
from the BBS 12 to the BCM 14, and from the BCM 14 to the BBS 12.
In an example embodiment, the BBS 12 is embodied as a simulator for
a 24-cell lithium ion battery commonly installed at an electrified
vehicle to provide traction power. Accordingly, the BCM 14 is in
the form of a battery control module for a 60-cell lithium ion
battery configured to perform various functions, such as, but not
limited to, monitoring and reporting a state-of-charge for the
traction battery. Generally, a battery control module is disposed
within a battery pack when a battery pack is installed at an
electrified vehicle. Bidirectional energy exchange between the BBS
12 and the BCM 14 enables active cell-balancing features of a
battery system to be tested. In addition, as will be discussed in
greater detail herein, advantageous aspects of the BBS 12 make it
well-suited for hot plug testing of the BCM 14.
[0014] FIG. 2 shows a block diagram of an example configuration for
the BBS 12. A plurality of cell simulators 16.i, hereinafter
referred to as "cellsims", each of which is configured to represent
and simulate a single cell of an EV traction battery pack, can be
coupled to a voltage source 20. In the drawings, the index "i",
which can range from 1 to N, with N representing the total number
of cellsims provided by the BBS 12, distinguishes a first cellsim
16 from a second cellsim 16. However, it is understood that each
cellsim 16 has identical components. The total number N of cellsims
16 within the BBS 12 can vary, depending on the type of battery the
BBS 12 is configured to simulate. For example, to test a battery
control module for a 36-cell battery, a simulator having 36
cellsims is required. In an example embodiment, the voltage source
20 can be in the form of a DC power supply, such as a 24V power
supply, coupled to the cellsims 16.
[0015] A cellsim control module (CCM) 18.x (x=1 to M, M=total
number of control modules) can be disposed to control and monitor
the operation and output of the cellsim 16.i. In the drawings, the
value for "x" is used to distinguish among multiple identical CCMs
18. In an example embodiment, as shown in FIG. 2, the CCM 18.1 can
be coupled to two cellsims, 16.1 and 16.2; however other
arrangements in which the CCM 18 is coupled to one, or more than
two cellsims 16 are contemplated. The CCM 18 can comprise hardware,
software, firmware, or some combination thereof. In an example
embodiment, the CCM 18 comprises a computing device such as a
digital processor, and a computer-readable medium operatively
coupled to the digital processor having stored thereon logic for
sequences of instructions for said digital processor, the sequences
of instructions, when executed by said digital processor, cause the
processor to perform the various CCM 18 tasks.
[0016] During a testing exercise, a master controller 22, can be
configured to control the total voltage of, and provide a testing
sequence for, the BBS 12. For example, the master controller 224
can be in the form of a computing device coupled to the BBS 12 and
configured to impose variable voltage commands as part of a test
script. By way of example, the test script can include voltages
recorded during a drive cycle of an electrified vehicle so that
realistic conditions can be simulated.
[0017] FIG. 3 depicts an example circuit 30 for the BBS 12. In the
following discussion of FIG. 3, for the sake of brevity in the text
and clarity in the drawing, the indices "i" and "x" are omitted for
components other than the cellsims 16.1 and 16.2, and the CCM 18.1.
Furthermore, while aspects of the invention are discussed with
respect to cellsim 16.1, it is understood that the features and
advantages of cellsim 16.1 also apply to cellsim 16.2. Likewise, it
is understood that control operations performed by the CCM 18.1 for
the cellsim 16.1 are also performed for the cellsim 16.2 A 24V DC
power supply 31 can be configured to provide a source of DC power
for the BBS 12. By way of example, the power supply 31 is coupled
to each cellsim 16 by a positive voltage bus 32 and a negative
voltage bus 33. Energy from the cellsim 16.1 can be provided to the
BCM 14 via a link 40 that comprises a positive bus 42 and a
negative bus 43 that can terminate at connector terminals 44 and
45, configured for coupling the BBS 12 and the BCM 14. In an
example embodiment, the cellsim 16.1 comprises a bulk storage
capacitor (SC) 34, a bidirectional DC/DC converter (BDC) 36, and a
discharge capacitor 38.
[0018] The (SC) 34 can be sized to achieve desired performance
characteristics. In an example embodiment, the SC 34 is sized to
provide the energy necessary to cooperate with the discharge
capacitor 38 to provide a sufficiently large energy pulse that
simulates the pulse provided to a BCM when it is initially plugged
into a battery simulator. Prior art simulators often include a
power supply accompanied by some sort of bulk capacitors. A problem
of prior art simulators, however, is that bulk capacitors are often
included randomly rather than purposefully selected to satisfy
specific energy requirements. Making matters worse, in prior art
simulators, the bulk capacitor typically provides the only energy
storage capability. When the energy of the bulk capacitor is passed
through a DC converter to the battery control module, losses
inevitably occur due to the switches, magnetics, etc. associated
with the converter. Thus, prior art simulators generally are unable
to provide a sufficiently high pulse to replicate hot plug
conditions. The present invention includes a suitably sized bulk
capacitor that, together with the discharge capacitor 38, can more
effectively represent energy capacities at an actual traction
battery cell.
[0019] The BDC 36 enables the battery simulator 12 to both provide
energy to and receive energy from the BCM 14. Configuring battery
packs and control modules for active cell balancing capability is a
relatively recent innovation in the electrified vehicle industry.
Simulation of this feature requires a battery simulator to be able
to receive energy from a battery control module as well as provide
energy to a battery control module. Battery simulators or testers
of the prior art, designed for only unidirectional energy transfer
out from the tester, are unable to test this feature of a battery
pack control module. Via the link 40, energy can be exchanged in
both directions between the BDC 36 and the BCM 14. A first relay R1
can be disposed at the positive bus 42, and a second relay R2 can
be disposed at the negative bus 43 to controllably couple the BDC
36 and the discharge capacitor 38 to the link 40.
[0020] The discharge capacitor 36 can be controllably coupled to
the BDC 36 and the link 40 by a switch SW1. When the switch SW1 is
closed, the discharge capacitor 36 can receive and store energy
from the bidirectional converter 34. Closure of the relays R1 and
R2 while the switch SW1 is closed couples the discharge capacitor
36 to the output link 40. When the BCM 14 is connected to the BBS
12, energy stored at the discharge capacitor 36 can be released in
a large pulse to the BCM 14, simulating the type of energy release
that occurs when a battery control module is first plugged in to an
actual battery pack. Energy stored in the SC 34 can also be
released to the BCM 14 through the BDC 36. Opening the switch SW1
disconnects the discharge capacitor 36 from the link 40, while
allowing the BDC 36 to remain coupled to the link 40. The BBS 12
can be configured to transfer energy to the BCM 14 through the BDC
36 to simulate EV battery cell activity during an EV drive cycle.
Thus, the switch SW1 is configured to enable the BBS 12 to simulate
hot plug conditions in addition to electrified vehicle drive mode
conditions.
[0021] Current sensors M1 and M2 can be disposed to monitor current
flow between the cellsim 16 and the BCM 14 and provide feedback to
the CCM 18. In an example embodiment, current limiters, such as
positive temperature coefficient (PTC)1 and PTC2 can be disposed at
the link 40 to prevent current between the BBS 12 and the BCM 14
from becoming too high, providing protection for electronic devices
at each of the apparatus.
[0022] The CCM 18.1 can be configured to monitor and control
cellsim 16.1 and cellsim 16.2 state and operation. The CCM 18.1 can
be configured to receive the BDC 36 input voltage, i.e. the SC 34
voltage, through the SC1 and SC2 inputs. The CCM 18 can also be
configured to receive link 40 voltage via the V1 and V2 inputs, and
the link 40 current from the current sensor Im1 and Im2 inputs. The
CCM 18 can be configured to control BDC 36 operation through
control connections (not shown) with the BDC 36. By way of example,
the CCM 18.1 can be configured to control the power flow direction,
i.e. whether power is transferred from cellsim 16.1 to the BCM 14,
or from the BCM 14 to the cellsim 16.1, as well as the power
magnitude, through its control of the BDC 36. For example, energy
can be transferred from the SC 32 to the BCM 14 in one direction
across the BDC 36, and from the BCM 14 to the SC 32 in the opposite
direction across the BDC 36. The CCM 18.1 can use cellsim 16.1
input and output, as well as input from the master controller 22
(FIG. 2) to provide local control for the one or more BDC 36 to
which it is coupled.
[0023] The CCM 18.1 can also provide fault detection using input
from the link 40. In an example embodiment, the current sensors Im1
and Im2 provide high bandwidth monitoring of the link 40 current.
The CCM 18.1 can be configured to compare the current and voltage
at the link 40 to a predetermined threshold. If the link 40 current
and/or voltage is not within a predetermined acceptable range, the
CCM 18.1 can cooperate with the master controller 22 (FIG. 2) to
shut down BBS 12 operation. By way of example, the cellsim 18.1 can
open the relays R1 and R2 at the cellsim 16.1 and 16.2,
disconnecting the cellsims 16.1 and 16.2 from the BCM 14. The CCM
18.1 can be configured to send a fault message to the master
controller 22 via a data interface (not shown) between by them. In
an example embodiment, in response to receiving a fault message
from the cellsim 18.1, the master controller 22 can be configured
to command remaining cellsims 18.x to open their respective relays
R1 and R2, and can also power down the BBS 12. By monitoring the
current provided to the BCM 14 by the cellsims 16.1 and 16.2, and
providing a quick response when predetermined limits are violated,
the CCM 18.1 can protect the BCM 14 against damage, particularly
damage that can result when a failed module continues to receive
current. The CCM 18.1 can provide fault detection during all phases
of BCM 14 testing.
[0024] As mentioned above, the BBS 12 can be used to perform hot
plug testing of the BCM 14, as well as simulated vehicle drive
cycle testing, during which BCM 14 active cell-balancing capability
can be tested. FIG. 4 shows an example method 50 for hot-plug
testing of a battery control module coupled to a BBS of the
invention. At block 52, a cellsim can be coupled to an output link
configured to electrically couple a simulated cell with a battery
module. For example, the CCM 18.1 can close relays R1 and R2 of
cellsims 16.1 and 16.2, coupling the BDC 36 to the link 40,
enabling cellsim 16.1, 16.2 output to be provided at the respective
terminals 44 and 45. A CCM 18.x can perform this action, and other
actions described in the method 50, for each cellsim 16.i under its
control. At block 54, a cellsim discharge capacitor can be charged.
For example, the CCM 18.1 can close the switch SW1 at the cellsim
16.1, connecting the discharge capacitor 38 to the BDC 36, and do
the same for the cellsim 16.2. The CCM 18.1 can turn on the BDC 36
on so that energy can be provided to, and stored at, the discharge
capacitor 38. Charging the discharge capacitor 38 with the relays
R1 and R2 closed can also energize the link 40, providing a voltage
between the positive and negative buses 42 and 43 at the terminals
44 and 45. At block 56, a battery control module can be received at
a BBS. For example, the BCM 14 can be plugged into the BSS 12 at
the terminals 44 and 45. At block 58 an energy pulse can be
provided to a battery control module, for example, the BSS 12 can
provide a high energy pulse to the BCM 14. When the BCM 14 is
electrically coupled to the BSS 12, the discharge capacitor 38 can
release its stored energy to the BCM 14 as a large energy pulse,
simulating what occurs when a battery control module is plugged
into a traction battery. In general, a constant voltage is
maintained at an actual battery cell during a hot plug energy
pulse. Accordingly, the BBS 12 can be configured to do the same.
The inputs V1 and V2, IM1 and IM2 enable the CCM 18 to monitor
cellsim 16 output during a pulse. If the BCM 14 draws enough energy
out of the discharge capacitor 38 that the voltage on the link 40
decreases, the CCM 18 can turn on the BDC 36 so that a desired
constant voltage can be maintained. However, it is conceivable that
energy may be released too quickly for the CCM 18 to monitor and
respond in time to maintain a constant voltage during the pulse.
Accordingly, it is contemplated that the CCM 18 can be configured
to turn the BDC 36 on during a pulse, regardless of link 40
feedback, to ensure access to energy stored in the bulk storage
capacitor 34 so that a constant cellsim 16 voltage can be
maintained. At block 60, post pulse behavior of the BSS 12 can be
monitored and controlled. If a hot-plug test is successful, a
system comprising a coupled BBS and battery control module
typically reaches a steady-state condition where current draw at
the battery control module ceases after the initial energy pulse.
However, if a battery control module fails during a hot-plug test,
it may continue to draw a large current that, if left unchecked,
can significantly damage the battery control module. Using the IM1
and IM2 input, the CCM 18 is able to detect the continued large
current draw and is also able to detect a rapidly declining voltage
on the link 40 from the V1 and V2 input. At block 62, a decision
can be made as to whether a fault exists. The CCM 18 can compare
current and voltage feedback to predetermined thresholds to
determine whether a fault condition exists. At block 64, the BSS 12
can respond to any detected faults. By way of example, a fault
response by the CCM 18 can comprise shutting down a battery
simulator-battery control module system and triggering an operator
alarm at the BSS 12. For example, the CCM 18.1 can open the relays
R1 and R2 of the cellsim 16.1, decoupling the BBS 12 from the BCM
14. In addition, the CCM 18.1 can open the switch SW1 and turn off
the BDC 36. The CCM 18.1 can also provide a fault message to the
master controller 22, and trigger a fault alarm at the BBS 12 to
alert an operator. In an example embodiment, a test can end at
block 68 after a fault response is performed. At block 66, a
decision can be made as to whether a test has been completed. In an
example embodiment, a test can end when equilibrium conditions are
reached. For example, the CCM 18 can use voltage inputs V1 and V2,
and current inputs Im1 and Im2 to determine that a
simulator-battery control module system has reached
equilibrium/steady state conditions. Other ways of determining a
test is completed, including a CCM 18 receiving a "TEST COMPLETE"
message from the master controller 22, will occur to those skilled
in the art. If the test is not finished, the method 50 can continue
at block 60. If a test is completed, then the method 50 can
terminate at block 68. In an example embodiment, a battery
simulator of the invention can decouple a discharge capacitor from
an output link when a hot plug test is finished. For example, the
CCM 18.1 can open the switch SW1 at the cellsim 16.1 and 16.2 to
decouple the discharge capacitor 38 from the link 40. If no
additional testing is to be performed, the CCM 18.1 can turn off
the BDC 36 and open the relays R1 and R2 at the cellsims 16.1 and
16.2, decoupling them from the BCM 14. However, it is contemplated
that upon completion of a hot plug test, a drive cycle test can be
administered in which a battery simulator is tasked to replicate
conditions experienced by a traction battery during a vehicle drive
cycle. If so, after a discharge capacitor is decoupled from an
output link, relays coupling a cellsim to a battery control module
can remain closed.
[0025] FIG. 5 shows an example method 70 for drive cycle testing of
a battery control module. At block 72 a cell simulator can be
coupled to an output link of a battery simulator. For example, the
CCM 18.1 can close the relays R1 and R2 of the cellsims 16.1, 16.2,
coupling the cellsims 16.1 and 16.2 to the output link 40. In an
example embodiment, drive cycle testing does not include providing
energy to a BCM from a discharge capacitor. The CCM 18 can be
configured to check SW1 status and open it if it is closed, so that
the discharge capacitor 38 is decoupled from the BDC 36 and the
link 40, turning the discharge capacitor 38 OFF. At block 74 a test
command voltage can be received. By way of example, each CCM 18 can
receive a a battery pack voltage command from the master controller
22. As discussed previously herein, the battery pack voltage
command can be based on voltage data recorded during a drive cycle
of an electrified vehicle. At block 76 a cellsim command voltage
can be provided. In an example embodiment, each BCM 18 of the BBS
12 can be configured to use the voltage command received from the
master controller 24 to determine a command voltage for the one or
more cellsims 16 to which it is coupled. By way of example, the CCM
18 can be configured to determine a voltage command for each
cellsim 16 by dividing the total battery pack command voltage by
the number of simulated cells at a battery simulator.
[0026] Having determined a cellsim command voltage, the CCM 18.1
can cause the cellsim 16.1 to provide the cellsim command voltage
across the terminals 44, 45 of the voltage link 40. By way of
example, the CCM 18.1 can use the V1 and V2 inputs for the cellsim
16.1 to detect the voltage present at the output link 40. The CCM
18.1 can be configured to operate the BDC 36 of the cellsim 16.1 to
increase or decrease the cellsim voltage as necessary to comply
with the cellsim command voltage. If the present cellsim 16.1
voltage is less than the cellsim command voltage, the CCM 18.1 can
be configured to turn on the DC converter 36 of the cellsim 16.1 to
boost the voltage at the output link 40. If the output link 40
voltage is greater than the cellsim command voltage, the CCM 18.1
can be configured to turn off the BDC 36, and allow current drawn
by the BCM 14 to reduce the voltage at the link 40 until the
cellsim command voltage is reached. The CCM 18.1 can control the
BDC 36 operation as necessary to maintain the cellsim command
voltage.
[0027] As discussed previously, a battery control module may be
designed to perform active cell-balancing in which energy received
from a battery pack, rather than being dissipated as heat, is
returned to the battery pack. Accordingly, in an example
embodiment, the BBS 12 is configured to cooperate with the BCM 14
to perform active cell-balancing in which energy transferred to the
BCM 14 from the BBS 12 to achieve a command voltage can be returned
to the BBS 12. In an example embodiment, energy released from a
first "donor" cellsim can be provided to a second "receiver"
cellsim, which preferably is controlled by the same CCM 18. For
example, the CCM 18.1 can be configured to cooperate with the BCM
14 so that energy provided to the BCM 14 from the cellsim 16.1 can
be provided to the cellsim 16.2, and vice versa.
[0028] For example, in response to a received battery pack command
voltage, the CCM 18.1 can turn on the BDC 36 of the cellsim 16.1 so
that energy is transferred from the BBS 12 to the BCM 14 by output
current at the link 40. By way of example, the energy can be stored
at a storage inductor (not shown) at the BCM 14. After a period of
inductor charging, the CCM 18.1 can turn off the BDC 36 of cellsim
16.1. The CCM 18.1 can turn on the BDC 36 of the cellsim 16.2 so
that energy received from the BCM 14 via input current at the link
40 can be provided to, and stored at, the SC 34 of cellsim 16.2.
The CCM 18 can monitor SC 34 voltage via the inputs SC1 and SC2. In
an example embodiment, the BDC 36 of the cellsim 16.2 can be turned
off when a predetermined maximum voltage is reached at the SC 34,
or when energy stored at a BCM 14 inductor is expended, a condition
detectable from the inputs IM1 and IM2. The energy stored at the SC
34 can be used to comply with a subsequent cellsim command
voltage.
[0029] At block 78 a determination can be made as to whether a
fault condition exists. By way of example, each CCM 18 can monitor
cellsim input/output via the V1, V2, IM1 and IM2 inputs to ensure
that a cellsim command voltage is maintained, and to detect faults
that may occur. For example, falling voltages and/or large current
draws can be indicative of a fault at the BCM 14. Voltage and
current levels can be compared to a predetermined fault threshold.
If a fault is detected, the BBS 12 can perform a fault response at
block 80. Example fault responses can include opening relays R1 and
R2, turning off the BDC 36 of one or more cellsims 16, and
triggering an operator alarm at the BBC 12. In an example
embodiment, a test can end at block 84 after a fault has been
detected and a fault response has been performed. However, it is
contemplated that in an alternative embodiment, a plurality of
thresholds can be used to determine whether a fault is significant
or insignificant, and a method can continue to block 82 if a
detected fault is not significant.
[0030] At block 82 a determination can be made as to whether
testing is finished. By way of example, an end test signal can be
received from the master controller 22 when a testing script is
finished. If an end test signal is received, the method can proceed
to block 84 where the method 50 can end. In an example embodiment,
the method 50 can conclude with a shutting down of a battery
simulator. For example, each CCM 18 can open relays R1 and R2, and
turn off the BDCs 36 of the cellsims 16 under its control. If a
test is not finished, the method can continue at block 74 and an
additional BBS command voltage can be received. Thus, the invention
provides a battery simulator, or battery tester, that combines the
energy storage advantages of bulk capacitor simulators with the
responsiveness advantages of DC power supply based simulators.
Accordingly, a battery simulator can be used for both hot plug
testing and drive cycle testing of a battery control module for an
electrified vehicle. In the past, battery testers were unable to
provide the high energy pulse that occurs when a battery control
module is plugged into an actual battery. As a result, battery
control modules that tested successfully, often failed when
actually installed at a vehicle. In the present invention, a
switchable discharge capacitor can store and release the energy to
simulate an actual hot plug pulse. Energy provided by a discharge
capacitor can be supplemented by energy stored at a bulk capacitor
when a DC/DC converter is turned on. When a drive cycle test script
is administered, the discharge capacitor can be switched off, i.e.
disconnected from an output link, and energy provided by a DC
converter can be used to provide a test script command voltage.
[0031] Equipped with a bidirectional DC-DC converter, a
bidirectional battery simulator can be configured to test active
cell-balancing capability of a battery control module since it can
both transfer energy to and receive energy from, the battery
control module. A further advantage of the present invention is its
improved ability to simulate battery cell current. Prior art
battery testers typically provide current of only a few milliamps,
much less than that provided by most actual traction battery cells.
The present simulator can provide currents of 2 or more amps,
better imitating the dynamics of an actual traction battery. In
addition, a battery simulator of the present invention can provide
improved protection for a battery control module being tested. A
control module configured to provide local control for simulated
cells of a tester can monitor both voltage and current at the link
coupling the tester with a battery control module. If a fault is
detected, the tester can be decoupled from the battery control
module to mitigate damage incurred as a result of the fault
condition.
[0032] As required, illustrative embodiments have been disclosed
herein, however the invention is not limited to the described
embodiments. As will be appreciated by those skilled in the art,
aspects of the invention can be variously embodied, for example,
modules and programs described herein can be combined, rearranged
and variously configured. Methods are not limited to the particular
sequence described herein and may add, delete or combine various
steps or operations. The invention encompasses all systems,
apparatus and methods within the scope of the appended claims.
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